Phoenix observes ice sublime on Mars

New data sent back from the Mars Phoenix lander has revealed strong evidence …

On Sol 20, the Phoenix Lander's 20th day on Mars, it observed some small bright objects in a recently dug trench. On Sol 24, they were gone. The small bright spots are now believed to be ice that sublimed—went directly from the solid phase to a gas.

Images: NASA/JPL-Caltech/University of Arizona/Texas A&M University

According to Principal Investigator Peter Smith, "These little clumps completely disappearing over the course of a few days, that is perfect evidence that it's ice. There had been some question whether the bright material was salt. Salt can't do that." Found in a trench known as "Dodo-Goldilocks," the ice chunks can be seen in the lower right portion of the image below in one frame, but they do not exist in the next.

Further evidence comes from other nearby trenches that the lander has dug. Images of these show a hard layer at a depth similar to where the ice was found in Dodo-Goldilocks. According to Ray Arvidson, one of the investigators working on the robotic arm, "We have dug a trench and uncovered a hard layer at the same depth as the ice layer in our other trench." While not as conclusive as the subliming objects, it suggests that the ice discovery was not exceptional for the area Phoenix finds itself in. The lander still has about two months of time left to work on the Martian surface, so NI will try to keep our readers informed of any and all further discoveries.

Matt Ford / Matt is a contributing writer at Ars Technica, focusing on physics, astronomy, chemistry, mathematics, and engineering. When he's not writing, he works on realtime models of large-scale engineering systems.